1. Field of the Disclosure
The present disclosure relates to an apparatus and method for maintaining consistent rotational speed of a rotary nozzle sprinkler with viscous damping when the arc of coverage is adjusted resulting in varying water flow rates.
2. Related Art
Rotary sprinklers using viscous dampening have been in use in the irrigation industry for more than fifteen years. Viscous damping resistance is provided to apply a specific amount of friction to counter movement of a deflector of the rotary sprinkler when a force is applied to it. Viscous damping has several advantages over gear driven sprinklers or impact sprinklers. For example, viscous damped sprinklers have fewer moving parts and a longer life. One drawback of viscous damped sprinklers is the inability to control the speed of rotation over varying water flow and pressure ranges.
Today, in the sprinkler industry, there are several manufacturers of rotary nozzles. These rotary nozzles use viscous damping, which is known in the art, to limit the speed at which the sprinklers rotate. Viscous damping relies upon oils or greases to create friction to limit sprinkler rotation speeds. Viscous damped units, however, typically are unable to maintain a consistent rotational speed over a wide range of pressure and flow rates. Another problem may arise when a small arc of coverage is selected, where the viscous damped sprinkler will have a very low flow rate. The low flow rate may not provide enough kick, or rotational force, to rotate the deflector and the rotary nozzle will stop rotating or stall.
Water deflection at the discharge point is what typically determines the power and rotational speed. Viscous damped rotary nozzles utilize a deflector with multiple fixed angular slots, or channels, which discharge the water off the deflector in streams. As the water is discharged from the internal valve it strikes the deflector and force is exerted on the deflector supplying the power to rotate the deflector while the viscous oil limits the speed of the turning deflector. The limitation of the current designs on the market is that as the arc of coverage increased, the flow against the deflector increases to maintain matched precipitation. This results in an increase in the rotational speed of the deflector because there are more streams of water and more force exerted on the deflector. Currently, in the industry, contractors and consumers have to purchase rotary nozzles in fixed patterns 90, 180, 270, and 360 degrees or nozzles that have limited adjustable range. These units in order to maintain speed over different flow rates all have unique deflectors to compensate for the amount of water to control the speed. The limitation with these conventional units that are currently on the market is that if the flow or pressure is changed, the rotation speed of the sprinkler increases or decreases. That is, there is no mechanism to change or control the rotational speed. A few manufacturers offer adjustable units that are adjustable only through a limited range, not 80 to 360 degrees.
Accordingly, it would be desirable to provide a deflector of a rotary sprinkler that avoids these and other problems.